As the demand for interconnectivity increases, more and higher-speed network and internetwork connection are made. One example is the increase in fiber optic networks that provide higher-bandwidth connections. Many networks transfer data according to synchronous data transmission standards. For examples, signals on fiber lines may be transmitted over the fiber lines according to the Synchronous Optical NETwork (SONET) or Synchronous Digital Hierarchy (SDH) standards.
Often fiber cables are interconnected in ring topology. A system of fiber cables is run between individual network elements (NEs), such as an Add/Drop Multiplexer (ADM). The interconnection between the discrete NEs provides a complete loop to provide better protection against failure of any interconnection between two discrete NEs on the network. Because of the looping nature of the network, i.e., the ring interconnections on the SONET/SDH network, if a given interconnection on the network were to fail, an alternate path would be available to provide routing for signals. The SONET/SDH networks including their associated rings are terminated in a central office (CO) or other switching center, to provide interconnection across rings to allow an NE to communicate outside its particular ring.
For every SONET/SDH ring terminated at the CO, there is traditionally a central office ADM. The central office ADM terminating the ring is generally called a Gateway Network Element (GNE), acting as the gateway communication path for signals interconnecting with the ring. When a GNE ADM is used to terminate each ring, each such ADM is interconnected with other devices in the CO via fiber patch panel or coax patch panels. Other devices in the CO may include other GNE ADMs, Digital Cross-connect Systems (DCSs), and packet switches. Some traffic is dropped locally from the patch panels to equipment within the same CO.
FIG. 1 illustrates a prior art CO as described. CO 101 has a GNE ADM 111 and 121 for each ring in networks 110 and 120, respectively. Note that each network 110 and 120 may include multiple SONET/SDH rings, as depicted in FIG. 1. To interconnect the rings in the networks shown, traditional systems have required the use of break-out panels. Break out panels, such as patch panel 130 uses a dedicated coax or fiber line to be run from the termination ADM to the panel, and a corresponding dedicated link from the panel to the switches. Thus, there is no inter-ring intelligence, and traffic from different rings cannot be directly switched. Patch panel 130 may be one or multiple physical devices that interconnect ADMs 111 and 121 to each other, or with other elements within CO 101. Patch panel 130 may include fiber patch panels and/or coax patch panels (e.g., DSX-3, meaning a Digital Signal Cross-connect for DS-3 (Digital Signal-level 3, 44.736 Mbps) signal switching).
Patch panel 130 interconnects with TDM (Time-Division Multiplex) cross-connect system 140 and packet switch 150. Traffic on networks 110 and 120 may include TDM and PDU (Protocol Data Unit, i.e., packet-switched) traffic. Traditional CO systems, such as system 100, switch TDM and PDU traffic in separate switching systems. Thus, ADMs 111 dedicated to carrying TDM traffic are interconnected via patch panel 130 to TDM cross-connect system 140, which will have a TDM switching fabric appropriate for providing deterministic routing of TDM traffic (using deterministic circuit-switched routing). In a similar fashion, ADMs 111 dedicated to carrying PDU traffic are interconnected via patch panel 130 to packet switch 150, which will have a packet-switched fabric for switching packetized data.
Some traffic in system 100 will be dropped locally to other devices within CO 101. ADMs 111 and 121 are interconnected to such local elements, illustrated as local dropped traffic 180, via patch panel 130.
It will be appreciated that the volume of interconnections requires a great deal of equipment and space. There is also a proportional need for power to operate all the equipment placed in the CO, as well as costs associated with upkeep of system 100. For example, adding or eliminating network elements may require service to CO 101 that could require multiple physical links to be nm with cables, often requiring running of cables over many floors of a building. Each such NE requires connection to a patch panel and/or break-out box.
Note also that each element of CO 101 requires a separate connection with management systems 170. Thus, management network 160 is shown connected to TDM fabric TDM cross-connect system 140, packet switch 150, and each individual GNE ADM 111 and 121 (shown by the multiple interconnection lines of 161 and 162) in CO 101. Management systems 170 have separate connections through management network 160 for each separate device. The collection of SONET/SDH rings 110 and 120 are each treated as a disparate network. There is no ring-to-ring knowledge or intelligence sourced from CO 101.
Thus, to communicate to ADM 112 on network 110, a discrete connection from management systems 170 carries a signal through management network 160 to GNE ADM 111, which forwards the signal to ADM 112. A similar pattern is followed to communicate with ADM 122 on network 120. Note that ADMs 111 and 121 are shown as potentially multiple devices, because multiple rings may be present in networks 110 and 120. Each of these multiple GNE ADMs represented by ADMs 111 and 121 are unable to communicate with each other directly.
Another drawback with system 100 is that management system 170 cannot derive a complete network topology of the networks connected to CO 101. Equipment such as ADMs 111 and 121 are available from a variety of vendors, and each vendor's equipment may or may not be interoperable with equipment from another vendor. One such condition giving rise to the lack of native interoperability is that equipment may use different management protocol schemes. Different protocol channels are possible over the Data Communications Channel (DCC) network that interconnects ring termination equipment. Two popular protocols currently used are Internet Protocol (IP) and Open System Interconnection (OSI), including different implementations of these base protocols. Traditional methods of dealing with differing protocols at best has involved tunneling one protocol through the other, which means there will be certain elements that will not be “visible” to the network management.